/Engine/Plugins/Online/OnlineFramework/Source/Lobby/Public/LobbyBeaconClient.h
Client notification that another player has left the lobby
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(Client, Reliable) virtual void ClientPlayerLeft ( const [FUniqueNetIdRepl](API\Runtime\Engine\GameFramework\FUniqueNetIdRepl) & InUniqueId )